As interpreted here, Lolium comprises five species that are native to Europe, temperate Asia, and northern Africa. All have been introduced to the Flora region, often as forage grasses; most have become established.

Lolium used to be included in the Triticeae, but evidence from genetics, morphology, and other studies shows its closest relationship to be to the species included here in Schedonorus. Artificial hybrids have been produced among L. perenne, L. multiflorum, Schedonorus pratensis, and S. arundinaceus. Cultivars of these crosses have been registered for commercial use and are sometimes used for forage. Natural hybrids are not uncommon in Europe.

Lolium perenne, a Eurasian species, is now established in disturbed areas throughout much of the Flora region. It is commercially important, being included in lawn seed mixtures as well as being used for forage and erosion prevention.

Lolium perenne intergrades and is interfertile with L. multiflorum; it also intergrades with L. rigidum. Typical L. perenne differs from L. multiflorum in being a shorter, longer-lived perennial with narrower leaves that are folded, rather than rolled, in the bud. Hybrids between the two species are called Lolium ×hybridum Hausskn.

Lolium multiflorum, a European species, now grows in most of the Flora region. It is planted as a cover crop, as a temporary lawn grass, for roadside restoration, and for soil or forage enrichment; it often escapes from cultivation, becoming established in disturbed sites.

Lolium multiflorum and L. perenne are interfertile and intergrade. Lolium multiflorum differs from L. perenne in being a taller, shorter-lived perennial or annual with wider leaves that are rolled, rather than folded, in the bud. Hybrids between the two species are called Lolium ×hybridum Hausskn. Lolium multiflorum also hybridizes with L. rigidum; those hybrids are called Lolium ×hubbardii Jansen & Wacht. ex B.K. Simon.

Lolium temulentum subsp. remotum is native to Europe, Asia, and northern Africa. It originated as a weed in flax fields, through unintentional selection for seeds that could not be separated from flax seed using early harvesting techniques. It is a rare weed in the Flora region, being reported only from southern Ontario and California, where it grows in waste places and fields.

Lolium temulentum subsp. temulentum is found occasionally in disturbed sites throughout much of the Flora region. It is native to the Eastern Hemisphere, where it is known only as a weed, especially of grain fields. Awn presence or absence and length vary, and have no taxonomic significance.

The seeds sometimes become infected with an endophytic fungus, assumed to be the source of the toxic pyrrolizidine alkaloids loline, 6-methyl loline, and lolinine, but not temuline, which is now considered an artifact of isolation (Dannhardt and Steindl 1985). Because primitive agricultural practices could not separate seeds of Lolium temulentum from those of wheat, infected seeds often resulted in poisonous flour.

Lolium persicum, a native of southwest Asia, has been found as a weed in grain fields and waste places in southern Canada, Montana, North Dakota, and Wyoming and, as an adventive, in New York and Missouri. It is now one of the top ten weeds of western Canadian cereal crops. It first became established in North America in Cavalier County, North Dakota, prior to 1910 (Dore 1950).